Earth’s Gravity Never Turns Off! Using Thought Challenges/Checks and Visual Cueing via Double-Shafted Arrows for Acceleration

• Autores: Anne Tabor-Morris
• Localización: The Physics Teacher, ISSN 0031-921X, Vol. 61, Nº. 8, 2023, págs. 675-679
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Introductory physics students frequently confuse concepts of velocity and acceleration, as in the example of a projectile motion problem where an object (e.g., a ball) is tossed upward in a gravitational field and undergoes freefall. Students often struggle especially with the fact that the ball’s acceleration is constant (not zero) at the highest point in the ball’s trajectory, the moment when the ball reverses its y-directional motion. First, I advise presenting students with thought challenges regarding acceleration due to Earth’s gravity—specifically asking students to consider what if “Earth’s gravity could just turn off ” (it cannot)—and recommending thought-check reminders to students for subsequent similar problems. Confusion also is due to new learners often mixing up velocity and acceleration vectors. So secondly, to help students distinguish between diverse types of vectors, I suggest consistently using distinct styles of arrows for velocity (single-shafted arrow →) and for acceleration (double-shafted arrow ⇒) (see Fig. 1). Jerk may be denoted by a triple-shafted arrow, as it is a third derivative (which is appreciated by calculus students), and so on for snap and higher orders, if discussed. To further support visual cueing, distance might consistently be depicted differently, such as with a very thin single-shafted arrow, perhaps with a hollow arrowhead, although labeling may be adequate. Force vectors can be represented as large thick hollow arrows. Several scenarios are highlighted here.